1. Field of the Invention
This invention relates to a method of improving the ground and an apparatus used therefor to improve water retention characteristics of soil.
More particularly, the invention relates to a method of improving the ground and an apparatus used therefor which has the steps of forming a water impermeable layer in the lower layer of the ground and mixing a water absorption polymer in the soil of the region of the upper layer of the water impermeable layer.
2. Description of the Prior Art
In a dry district such as a desert zone or the like, the water content is insufficient in an environment in which plants are difficult to be bred.
In the dry district, the concentration of salts dissolved out from soil in underground water tends to be increases. Not only ground surface water but underground water moved to the ground surface by a capillary phenomenon are lose their water content by evaporation, and salts contained therein remain on the ground surface. Even if a part of the salts on the ground surface is dissolved in rainy water and again dissolved in the underground water, it is repeatedly moved to the ground surface with underground water to be moved by the capillary phenomenon. Thus, since the evaporated amount of the water content on the ground surface is much, the salts remain and accumulate on the ground surface so that the breeding of plants is disabled with salt detriments.
In a dried sand soil zone such as a sand dune, sand dusts are easily generated by wind power, and the ground configuration is varied thereby.
Heretofore, in order to prevent sand dust, means such as sand preventive forest, sand preventive bank is provided. However, these means necessitates a large quantity of labor, cost and time, but the effect is limited.
On the other hand, a number of techniques for accelerating bleeding of plants by utilizing water retention characteristics of a water absorption polymer have been proposed as shown in, for example, Japanese Patent Laid-Open (KOKAI) Nos. 58-76005, 57-33508, 57-79802, 58-149604, 58-155005, 59-34822, 59-48007, 60-188003, 62-201523.
However, all of these techniques are to aid supplementation of water content by mixing a water absorption polymer with soil in a range affecting the roots of plants.
There is no known technique for breeding plants by forming a water impermeable layer in the lower layer of the ground and interrupting the movement of underground water of high concentration of salts to the ground surface to thereby prevent salt detriments.